Tobacco smoke filter

ABSTRACT

A method and apparatus for making tobacco smoke filter means having totally enclosed inner cavities surrounded completely by the filtering material. Selected cavities may be filled with a sorbent smoke-modifying additive or the like in order to provide both gas phase filtration and solid phase filtration to the resultant product. Filter rods are manufactured by utilizing a reciprocating mandrel which is timed to the movement of a filtering material, such as a continuous cellulose acetate filamentary tow, through processing stations, particularly a steam-treating bonding station, with an annular wall of smokepermeable bonded fibrous members of the filtering material being formed when the mandrel is in its forward-most position extending at least to the point where the bonding agent contacts the filtering material. At the rearward-most portion of the stroke of the mandrel the filtering material is permitted to extend transversely completely across the bonding zone before being contacted with the steam so as to form a smoke-permeable plug of filtering material before and after the annular wall portions, thereby defining the internal cavities. Selected cavities may be partially or completely filled with an additive passing through the mandrel which can be hollow, as the mandrel is withdrawn during its rearward stroke.

United States Patent 1191 Berger 1 TOBACCO SMOKE FILTER [75] Inventor:

22 Filed: Jan. 17, 1974 211 App]. No.: 434,223

Related U.S. Application Data [62] Division of Ser. No. 287,803, Sept.11, 1972, Pat.

[52] U.S. Cl. 93/1 C, 93/77 FT, 131/261 A [51] Int. Cl. A24c 5/50 [58]Field of Search 93/1 C, 77 FT; 131/253, 131/254, 255, 261 A [5 6]References Cited 1 UNITED STATES PATENTS 2,190,107 2/1940 Pohle 131/12 X2,277,686 3/1942 Blount 131/255 X 3,096,772 7/1963 Korber 131/13 X3,637,447 1/1972 Berger et a1. 93/1 C X Primary ExaminerRoy LakeAssistant Examiner-James F. Coan Attorney, Agent, or FirmHolman & SternRichard M. Berger, Richmond, Va.

[ Nov. 12, 1974 [5 7] ABSTRACT A method and apparatus for making tobaccosmoke filter means having totally enclosed inner cavities surroundedcompletely by the filtering material. Selected cavities may be filledwith a sorbent smoke-modifying additive or the like in order to provideboth gas phase filtration and solid phase filtration to the resultantproduct. Filter rods are manufactured by utilizing a reciprocatingmandrel which is timed to the movement of a filtering material, such asa continuous cellulose acetate filamentary tow, through processingstations, particularly a steam-treating bonding station, with an annularwall of smoke-permeable bonded fibrous members of the filtering materialbeing formed when the mandrel is in its forward-most position extendingat least to the point where the bonding agent contacts the filteringmaterial. At the rearward-most portion of the stroke of the mandrel thefiltering material is permitted to extend transversely completely acrossthe bonding zone before being contacted with the steam so as to form asmoke-permeable plug of filtering material before and after the annularwall portions, thereby defining the internal cavities. Selected cavitiesmay be partially or completely filled with an additive passing throughthe mandrel which can be hollow, as the mandrel is withdrawn during itsrear,- ward stroke.

9 Claims, 15 Drawing Figures 4 ADDlTlVE 7 some PATENTEDNUV 12 197:3,847,064

SHEET 1 Bf 2 ADDFUVE 74x SOURCE STEAM V 4O '26 52 vii/III '14 $6 68 ea gl T as l TOBACCO SMOKE FILTER This is a divisional, of application Ser.No. 287,803, filed Sept. 1 1, 1972 now U.S. Pat. No. 3,811,451.

This invention relates to the production of filter means and relatesmore particularly to tobacco smoke filter elements. More specifically,the instant inventive concepts are primarily concerned with producingfilter means for cigarettes, although the products of this invention aregenerally useful as filters, particularly for tobacco smoking means,whether they be cigarettes, cigars, pipes or the like. Since filters forcigarettes are particularly commerically important, the basicembodiments of the instant invention will be discussed as they relate tothe production of filtered cigarettes.

Various prior art techniques are known for making filters for use inconnection with cigarettes, and the like, although the resultingproducts, in general, have one or more disadvantages. Perhaps the mostimportant property of a filter means is its efficiency, that is, itsability to remove undesirable constituents from tobacco smoke.Filtration efficiency is ordinarly measured in terms of the percentageof total particulate matter (TPM) removed from the smoke, although thereis also some concern for the percentage of gas phase constituents whicha filter means is capable of removing. While filtration efficiency isperhaps the most important property of cigarette filter means, it hasbeen necessary, with prior art filter devices, to compromise thefiltration efficiency in order to provide such filters with otherproperties, such as pressure drop, taste, hardness, appearance and cost,which are important from the stand-point of commerical acceptability.For example, the most commonly utilized cellulose acetate filter meanshas a relatively low filtration efficiency since increased efficiencycan only be obtained either by increasing the density of the filtermaterial or the length of the filter element, both of which produce apressure drop across the filter which is excessive and unacceptable froma commercial stand-point. While various suggestions have been madeforthe production of filter means which have improved filteringproperties, such prior art developments, for the most part, have notbeen commercially acceptable either because the resulting filter meanshave been found to have objectionable taste" characteristics wherebycigarettes provided with such filtering means fail to satisfy a largesegment of the smoking public, or because the techniques and/or thematerials utilized in the production of such filter means have increasedthe cost excessively.

High filtration efficiency is considered by the industry to be removalof 60 percent or more of total particulate matter. Cigarette filtershaving such properties are presently being produced in accordance withthe teachings of U.S. Pat. Nos. 3,533,416, 3,599,646, and 3,648,71 1.Yet, the production of a cigarette filter having even a slightlyincreased filtration efficiency, without detrimentally affecting otherdesirable properties, e.g. pressure drop and the like, would becommercially important. Moreover, the production of a cigarette filteror the like having equivalent filtration efficiency, but utilizingsubstantially less material, therebyminimizing the cost ofmanufacturing, would also be quite commercially important. It isextremely significant to be able to provide improved filtrationefficiency for a given level of pressure drop. Moreover, it is highlyde- I enable the manufacture of filter means for cigarettes and the likewherein the filtration efficiency is increased for a given level ofpressure drop.

A still further object of this invention is to provide methods for themanufacture of cigarette filter means which are simple and inexpensiveto operate, while enabling high speed operation and whichutilizerelativel'y small amounts of filtering materials since a largeproportion of the filtering material in each filter means is availableto perform its primary function, that is, removal of undesirableconstituents from smoke.

Another object of this invention is to provide a cigarette filter meanswhich may have various characteristics, includingboth particulate matterfiltration efficiency as well as gas phase filtration efficiency, ifdesired.

A further basic object of this invention is to provide for theproduction of cigarette filter means which may have variousconfigurations to provide the final filtered cigarette with anaesthetically pleasing appearance.

Other and further objects of this invention reside in the chemical andphysical characteristics of the filter product as well as themanipulative steps utilized in the production and the various featuresof construction found in the manufacturing apparatus. Still otherobjects will in part be obvious and in part be pointed out as thedescription of the invention proceeds, and as will be seen from theaccompanying drawings wherein:

FIG. 1 is an enlarged longitudinal cross-sectional view showing aportion of a method and means for producing filter elements according tothe instant inventive concepts, selected elements being shown inalternate positions in dotted lines;

FIG. 2 is a schematic cross-sectional viewshowing the depositionof anadditive into alternate cavities of a filter rod as it is beingproduced;

FIG. 3 is a longitudinal cross-sectional view through one form of filterrod that can be produced according to the instant inventive concepts,showing how such a rod can be sub-divided to provide individual filterelements of selected characteristics;

FIG. 3A is a schematic view of a portion of a processing line forcrimping, overwrapping and severing a rod formed by the instantinventive concepts;

FIG. 4 is an enlarged perspective view, partially in cross-section,showing a portion of a filtered cigarette incorporating a filter elementaccording to one embodiment of the instant inventive'concepts, partsbeing broken away for illustrative clarity;

FIG. 5 is a longitudinal cross-sectional view through FIG. 6 is atransverse cross-sectional view taken substantially along lines 6-6 ofFIG. 5;

FIG. 7 is an enlarged perspective view, partially in cross-section,through yet another modified form of filter element according to theinstant inventive concepts; and

FIGS. 8-14 are elevational views of various filter elements which can bemade in accordance with the instant invention, having differentconfigurations for aesthetic and functional purposes.

Like reference characters refer to like parts throughout the severalviews of the drawings.

Before proceeding in detail to a discussion of the specific methods,means and products of the instant invention, reference is made to theaforementioned United States Patents, the subject matter of which isincorporated herein in their entirety.

Referring particularly to FIG. 1 and to U.S. Pat. No. 3,637,447,commonly assigned with the instant application, it will be seen thatFIG. 1 of this application shows a portion of a slightly modified formof the apparatus shown in FIGS. 1 and 19 of U.S. Pat. No. 3,637,447. Theremaining portions of the apparatus according to the instant inventiveconcepts, as well as the techniques utilized, conform quite closely tothose shown in the aforementioned patent and reference may be had tothat disclosure for such details.

Although the products of this invention are preferably and primarilyformed from a continuous tow of cellulose acetate filamentary material,the instant disclosure is not to be limited to this concept, since withslight modifications obvious to those skilled in the art, filamentarytow formed of other materials such as polyethylene, polypropylene andthe like can be utilized, and, moreover, non-woven staple fibers of thetype described in some detail in U.S. Pat. Nos. 3,297,041 and 3,552,400,also commonly assigned, the disclosures of which are incorporated hereinby reference, may also be utilized. However, since cellulose acetatefilamentary tow is the preferred material from a commercial stand-point,the remainder of this specification will be directed to the use of suchmaterial.

With reference now to FIG. 1, a portion ofa method for forming filterelements according to the instant inventive concepts is designatedgenerally by thereferencc numeral 20 and the portion shown will be seento include air nozzle or. stuffer-jet 22 spaced along the path of travelof a filtering material 24 toward a first curing station 26.

The details of constructions of the stuffer-jet 22 correspond basicallyto the similar element designated 14 in U.S. Pat. No. 3,636,447, wherebyfurther details need not be incorporated at this point.

The first curing station 26 is similar in construction to the element 60in U.S. Pat. No. 3,636,447, although somewhat further details are shownin the instant application. Specifically, this first curing stationwhich may be referred to as a bonding zone includes a generallycylindrical portion 28 and a flared or conical entry portion 30.

Just as air is introduced into the stufferjet 22 through the conduit 32which communicates with a manifold 34 to be fed into the tow 24 in anannular direction, steam or other means capable of activating a bondingagent within the filtering material is introduced through a conduit 36into a manifold 38 from which it passes through a multiplicity of spacedapertures 40 into the two intermediate the path of travel of the towthrough the cylindrical portion 28 of the bonding zone 26.

Thus, it will be seen that an elongated band of filtering material24-enters the rearward end of the stufferjet 22 passing around a mandrelsupport 42 to form, at this point, a generally hollow tubular elementwhich continues to be moved forwardly around a mandrel 44 actuallydisposed within the stuffer-jet 22 and passing at least partially intothe bonding zone 26. As the tow emerges from the forward end of thestuffer jet 22 it is mixed with air supplied from the conduit 32.Adjustments of the various elements of the stuffer-jet 22 in the mannerdescribed in U.S. Pat. No. 3,636,447 creates a venturi-like opening atthe exit of the stuffer-jet 22 to cause the emerging tow to explode orbloom as shown at 46 into a uniformly random fluffy mass before passinginto the bonding zone or curing station 26.

lt should be pointed out that since the bonding'agentv inherent in thefilamentary tow is not activated during passage through the stuffer-jet22, the ultimate shape imparted to the tow which is formed of aplurality of plasticized random fibrous members, is not affected at thispoint.

It is not until the tow is contacted with'a bonding agent, in thisinstance, steam, that the fibrous members of the filtering material arebonded to each other at spaced contact points to form an elongated,smokepermeable, rod which defines a tortuous path for passage of smoketherethrough.

As will be seen, the heating and shaping apparatus for bonding zone 26is so constructed that'the moving tow which is being formed into agenerally rod-like shape is contacted with steam during its passagethrough the cylindrical portion thereof. The application of the steam tothe filamentary tow as it is gathered together results in a softening ofthe tow fibers and the plasticizer carried thereon and has the effect ofuniformly bonding the fiber members of the tow together at spacedpoints. By passing the steam into the tow under pressure in a confinedarea and preferably at an angle to the longitudinal axis in a directionopposite to the direction of movement of the tow, the steam enters thetow, between the fibers and contacts the fibers as they are beinggathered together. All of the fibrous members and all of the plasticizerare thus generally substantially uniformly heated whereby asubstantially uniform bonding at spaced contact points of the fibrousmembers if effected.

In the absence of the mandrel 44 a smoke-permeable generally cylindricalcontinuous rod would be formed as the tow passed through the firstcuring station 26. However, the presence of the mandrel 44 defineswithin the bonding zone 26 an annular space through which the filteringmaterial must pass thereby forming, instead of what may be called asolid rod, an internal cavity, that is, a hollow rod.

According to the teachings of U.S. Pat. No. 3,637,447, the product thatexits from the first curing station is, in fact, a continuous hollow orannular element. It is at this point that instant inventive conceptsdepart from the teachings of the aforementioned U.S. Patent.

As will be seen particularly in FIG. 1, the mandrel 44 is provided withmeans 48 which function to reciprocate the mandrel within its supportingelement 42, and more specifically, which function to reciprocate theforward end portion 50 of the mandrel 44 between a first position whichis at least as far forward in the path of travel of the filteringmaterial 24 as the point at which the filtering material is contacted bythe bonding agent, and a second position, designated by dotted lines 52spaced rearwardly of such point.

The reciprocating means 48 can comprise any mechanical constructioncapable of moving the mandrel 44 forwardly and rearwardly along the axisof the processing machinery. In the embodiment shown, which is intendedonly to be illustrative, a link 54 is pivoted at one end 56 to a bracket58 carried by the rearward portion of the mandrel 44 and is pivotedintermediate its ends as designated at 60 to some fixed support (notshown). The opposite end of the link 54 carries a cam follower or roller62 normally urged into contact with an eccentric 64 by a spring means66.

When the mandrel 44 is at its forward-most position it will be seen thatthe filtering material 24 is confined within an annular space betweenthe exterior of the mandrel 44 and the interior of the cylindricalportion 28 of the bonding zone 26. Since the filtering material iscontacted with steam or some equivalent bonding agent at this point, thefibrous members of the filtering material are formed into asmoke-permeable annular wall portion 68.

However, as the mandrel 44 is withdrawn on its return stroke to theposition where the forward end portion is located at the pointdesignated by the dotted lines 52 a portion of the filtering material ispermitted to extend transversely completely across the bonding zonebefore being contacted by the bonding agent. This is especially truewhen the point 52 is chosen to fall within the conical section 30 of thefirst curing station 26. In this manner, a smoke-permeable plug ofbonded fibrous members 70, which is integral with the annular wall 68,is formed as this portion of the filtering material is contacted by thebonding agent during its forward movement.

Of course, the various elements causing forward movement ofthe filteringmaterial and reciprocation of the mandrel must be synchronized and timedto provide for a proper relationship, depending upon the desiredfunctional characteristics of the product, but means to accomplish thisend are well within the ordinary skill of the art and need not be dealtwith in any great detail.

It will now be seen that the method and means described enable theproduction of intermittent internal cavities totally enclosed andsurrounded by the annular wall 68 and front and rear plugs 70.

According to a further feature of the instant inventive concepts, theinternal cavities can be filled or partially filled, or selectedcavities can be filled with an additive material, such as, for example,a sorbent smokemodifying material. To this end, the mandrel 44 maybemade hollow as shown in FIG. 1 and an additive source 74 can communicatewith the rear end of the mandrel 44 through a flexible conduit 76. Byany ordinary actuating means (not shown), a pre-selected quantity orcharge of additive material may be fed through the mandrel into one ormore selected cavities as the mandrel is being moved rearwardly duringits return stroke. Obviously, the operation of the additive feedingmeans can be so coordinated with the manufacture of the filter rod thatadditive material in any desired quantity can be fed into each and everycavity being formed, or only into selected, such as alternate, cavities.Moreover, the additive material may be particulate'in naturealternatively it may be a mixture of such materials and/ or liquidmaterials so long as they do not deleteriously affect the properties ofthe filter rod being manufactured.

The size of the cavities formed, the thickness of the annular wall, theextent of the plugs between the cavities, the use, level of charge, andtype of additive may all be readily varied well within the skill of theart. Additionally, once a filter rod is completely formed, as will beexplained in more detail hereinafter, it may be selectively sub-dividedat any point along its length such as shown,'for example, by the dottedlines 80 in FIG. 3 to form individual filter elements. Of course,ordinarily, severing of the filtering rod will not take place until ithas been overwrapped with paper or the like in a manner such asdescribed in U.S. Pat. No. 3,637,447, but it is of importance to notethat filter elements may be provided having a single internal cavity, oralternatively, a plurality of internal cavities, one or more of whichmaybe filled with an additive material so as to provide filter elementshaving any desirable combination of characteristics, depending upon theintended use therefor.

Subsequent processing of the filter rod may follow quite closely theprocedures outlined in U.S. Pat. No. 3,637,447. Thus, any desired meansmay be provided such as the common arrangement shown at in theaforementioned patent to continuously pull the filter rod through theprocessing apparatus shown in FIG. 1 of the instant application.Moreover, a subsequent curing station such as illustrated at 114 in U.S.Pat. No. 3,637,447 may be provided, particularly if the filter rod is tobe crimped as designated at 118 in that patent prior to being curedandoverwrapped in the conventional manner shown at 146 and 152 in U.S. Pat.No. 3,637,447.

In FIG. 3A an exemplary portion of a processing line for furthertreating the rod shown in FIG. 3 is illustratively shown. The rod isdesignated in FIG. 3A as element 200 and passes into a conventionalcrimping means 202 to produce the crimped rod 204 which is thenoverwrapped, for example, with a sheet of ordinary plug wrap such asshown at 206, by passing the crimped inner element 204 and the plug wrap206 through a means 208 wherein it is rolled in a wellknown manner withthe help of an endless belt 210. The lateral edges of the plug wrap 206may be secured together to form a longitudinal butt or lapped seamutilizing a conventional heat sealing means 212. The overwrappedcombined inner and outer elements may then be cut in any conventionalmanner as schematically shown at 214 to form segments 216.

During the overwrapping procedure it is quite important for a portion ofthe external surface of one of the plugs 70 of the filter rod to be incontinuous peripheral contact with the internal surface of theoverwrapping material. This forms a sealed area through which smokecannot pass. For a better understanding of such an arrangement referenceis made to FIG. 4 where a fragmentary portion of a filtered cigarette isdesignated generally by the reference numeral 1.00 and is seen tocomprise a conventional tobacco rod 102 overwrapped with cigarette paper104 and secured in end-to-end relationship with a filter elementaccording to the instant inventive concepts designated generally by thereference numeral 106. In the embodiment of filter element 106 shown inFIG. 4, the inner member which is a subdivided portion of the filter rodmanufactured accordin g to the techniques shown in FIG. 1 is referred togenerally as 108 and will be seen to comprise a plug 110 at themouth-piece end, the external surface of which is juxaposed to theinternal surface of the overwrapping material 112 to form theaforementioned sealed area. Finally, a tipping overwrap 114 isillustrated to secure the filter portion to the tobacco portion in aconventional manner. The annular wall of the filter element 106 will beseen at 116 as will the internal cavity at 118. In the embodiment shownin FIG. 4, one end of the filter element 106 has been crimped, in themanner described in U.S. Pat. No. 3,637,447 to form a plurality ofcruciform-shaped fins 120, the external or peripheral edges of which arein contact with the internal surface of the overwrapping material 112 inorder to assist in centering the inner member within the outer member.

By reference to FIGS. 8-14 alternate configurations for the crimped endof the filter element will be seen. In each instance, only the shape ofthe crimping means need be modified in order to provide the desiredconfiguration, again, a matter of design well within the skill of theart which needs no further explanation.

It should be recognized that the filter means according to thisinvention can be used either singly or doubly, or in fact in anymultiple units. For'example reference is made to the embodiments ofFIGS. 5 and 6 wherein it will be seen that the filter rod has beencrimped intermediate a cavity to form a plurality of independent cavitymeans 122, 124, with a crimped separating wall portion 126 therebetween.With the previous embodiments it was necessary for smoke passing fromone end of the filter element to the other to pass through the plug andinto the internal cavity, which has a lower resistance to passage ofsmoke than the filtering material itself, and then again out of thefilter element through the filtering material so that, in each instance,the smoke must pass at least twice through the filtering material.Moreover, in an embodiment such as shown in FIG. 4 where a portion ofthe filter element has been crimped to form an external cavity, in thisinstance, a multiplicity of external cavities 128, the smoke must alsopass through these cavities from the tobacco to the smoker. I

In contrast, with the embodiment of FIG. 5, the smoke must actually passfour times through the filtering material, considering the fact that itpasses through one of the end plugs, into the internal cavity 122,through the filtering material again into the external cavity 130, backthrough the filtering material into the internal cavity 124 and finallythrough the filtering material of the plug at the mouth-piece end of thefilter element.

The variations of the aforementioned arrangements are only limited bythe ingenuity of the processer, and in no way need depart from theinstant inventive concepts in order to result in filter elements of analmost infinite variety of functional and aesthetic properties.

The embodiment of FIG. 7 is quite similar to the previous embodiments,with the exception that it is provided with a plurality of external,longitudinally extending, cavities 132 formed between ribs 134 almost inthe manner of a gear. Of course, such cavities cannot extend the fulllength of the exterior of the filter element since it is necessary toprovide an uninterrupted circumferential surface at one end of thefilter element in order produce the necessary sealed area which forcesthe smoke through the filtering material and precludes by-passing. Thecavities 132 increase the external surface area of the filter elementpermitting a greater capability for the smoke to pass the length of thefilter element into the internal cavity, which in the embodiment of FIG.7 is shown as filled with a sorbent smokemodifying additive material.

It is to be noted that there are two quite important features of eachand every embodiment of filter element formed according to the instantinventive concepts. First of all it must be recognized that the primarypurpose of the filtering material is to function to eliminate or reduceundesirable constitutents from smoke passing therethrough, and withrespect to the fibers or filamentary portion of the filter element, itis especially the particulate matter or solid phase constitutents of thesmoke that are being affected.

A significant reduction in filtration efficiency results whenever thesmoke-permeable rod of filtering material is compressed or crimped andit is for this reason that each filter element according to the instantinventive concepts includes at least one end portion which is in theform of a smoke-permeable uncrimped plug, the outer surface of thisportion at least in part forming the sealed area with the overwrappingmaterial. By maximizing the uncrimped portion of the filter element,filtration efficiency is increased significantly, thereby permitting thefiltering material to perform its primary function in an optimum manner.

Another basic important feature of each filter element producedaccording to the instant inventive concepts is the presence of at leastone internal totally enclosed cavity means surrounded by the filteringmaterial. Heretofore it has not been possible to produce such aninternal cavity means wherein the filtering material that formed ordefined the cavity was integral both with respect to the end portionsand the annular or peripheral wall extending therebetween. By enablingthe production of a filtering element wherein the internal cavity iscompletely surrounded by integral filtering material which is notnecessarily crimped, nor otherwise secured together by extraneousmaterial such as adhesives and the like, the highest level of filtrationefficiency per unit of filtering material can be realized.

Thus the instant inventive concepts enable the production of a filterelement having increased filtration efficiency for a given pressuredrop, while retaining all of the other desirable characteristics ofcigarette filters, including such properties as taste, appearance'andminimized cost through simplicity in manufacturing techniques andapparatus as well as reduction in the quantity of filtering material fora given level of efficiency.

Again, it should be emphasized that filter elements of the type shown,for example, in FIG. 2 may be utilized by themselves, with no subsequentcrimping necessary, providing a plug of smoke-permeable materialextending transversely completely across each end of the filter elementwith, if desired, a sorbent smoke-modifying additive providedtherewithin during the manufacturing process in an extremely simplifiedmanner and by a technique which precludes channeling of the smoke pastthe additive particles increasing the gas phase efficicncy of the finalproduct as well. Alternatively, and for particular applications,crimping can be utilized to modify the appearance or functionalproperties of the filter means, again emphasising the versatility of theinstant inventive concepts, both from the standpoint of manufacturingand the final product characteristics.

Having now considered the foregoing detailed description it will be seenthat there is herein provided an improved method and means for producingtobacco smoke filters having all of the advantages set forthhereinabove, and others, including many features of great commericalsignificance.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A method of making smoke filter means comprismg:

a. providing a bondable filtering material including a multiplicity offibrous members;

b. continuously passing said filtering material into and through anelongated bonding zone and, intermediate the passage of said filteringmaterial through said bonding zone, contacting same with a bonding agentto bond said fibrous members of said filtering material to each other atspaced contact points thereby forming an elongated, smokepermeable, roddefining a tortuous path for passage of smoke therethrough;

c. during the passage of said filtering material through said bondingzone, positioning a mandrel generally axially of said bonding zone todefine an annular space through which said filtering material must pass;

(I. reciprocating said mandrel in timed relationship to the passage ofsaid filtering material through said bonding zone between a firstposition, at least as far forward in the path of travel of saidfiltering material as the point at which said filtering material iscontacted by said bonding agent, to thereby produce a smoke-permeableannular wall of bonded fibrous members as said filtering passes saidpoint, and a second position, sufficiently rearwardly of said point inthe path of travel of said filtering material to permit a portion ofsaid filtering material to extend transversely completely across saidbond- I ing zone before reaching said point, to thereby produce asmoke-permeable plug of bonded fibrous members as said filteringmaterial passes said point, said annular wall and said plug beingintegral with each other, whereby said rod is provided with intermittentinternal cavities totally enclosed and surrounded by said annular walland by plugs forwardly and rearwardly thereof;

e. overwrapping said rod with an overwrapping material so as tojuxtapose portions of the inner surface 3. A method according to claim 1further including the step of feeding a quantity of a sorbentsmokemodifying material through the mandrel during the rearward movementof the mandrel to at least partially fill selected internal cavitieswith the smoke-modifying material as said internal cavities are formed.

4. A method according to claim 3 wherein said smoke-modifying materialcomprises activated carbon.

5. A method according to claim 1 further including the step of crimpingselected portions of said rod before overwrapping same to form externalcavities between the exterior surface of said rod and the interiorsurface of said overwrapping material.

6. An apparatus for making smoke filter means comprising:

a. a source of a bendable filtering material including a multiplicity offibrous members;

b. means defining an elongated bonding zone;

c. means for continuously feeding said filtering material into andthrough said bonding zone;

d. means for feeding a bonding agent into said bonding zone and intocontact with said filtering material at a point intermediate the path oftravel of said filtering material through said bonding zone to bond saidfibrous members of said filtering material to each other at spacedcontact points, thereby forming an elongated, smoke permeable, roddefining a tortuous path for passage of smoke therethrough; v

e. elongated mandrel means having a forward end portion axiallypositioned within said means defining said bonding zone to define anannular space through which said filtering material must pass;

f. means for reciprocating said mandrel means within said bonding zonein timed relationship to the passage of said filtering material throughsaid bonding zone between a first position wherein said forward endportion extends at least as far forwardly in the path of travel of saidfiltering material as the point at which said filtering material iscontacted by said bonding agent, to thereby produce a smokepermeableannular wall of bonded fibrous members as said filtering material passesout said point, and a second position wherein said forward end portionextends sufficiently rearwardly of said point in the path of travel ofsaid filtering material to permit a portion of said filtering materialto extend transversely completely across said bonding zone beforereaching said point, to thereby produce a smoke-permeable plug of bondedfibrous members as said filtering material passes said point, saidannular wall and said plug being integral with each other, whereby saidrod is provided with intermittent internal cavities totally enclosed andsurrounded by said annular wall and by plugs forwardly and rearwardlythereof;

g. means for overwrapping said rod with an overwrapping material so asto juxtapose portions of the inner surface of said overwrapping materialwith continuous peripheral portions of the exterior surface of at leastportions of selected plugs to form sealed areas precluding passage ofsmoke thereacross; and I w h. severing means for transversely severingsaid overwrapped rod at selected locations to form filter elements eachof which includes at least one of said internal cavities and at leastone of said sealed areas.

7. An apparatus according to claim 6 wherein said means defining abonding zone comprises a cylindrical portion and a juxtaposed conicalentry portion rearwardly of said cylindrical portion in the path oftravel of said filtering material, said means for feeding said bondingagent into said bonding zone comprising a multiplicity of peripherallyspaced apertures opening into said cylindrical portion, said forward endportion of said mandrel means in said first position being located atleast as far forwardly into said cylindrical por tion of said bondingzone as the points at which said bonding agent is fed into said bondingzone, and said forward end portion of said mandrel means in said secondposition being located within said conical portion of said bonding zone.

8. An apparatus according to claim 6 wherein sai mandrel means ishollow, further including a source of a sorbent smoke-modifyingmaterial,- and means for feeding said smoke-modifying material throughsaid mandrel means and out of said forward end portion thereof into thecavities being defined in said rod on the rearward stroke of saidmandrel means.

9. An apparatus according to claim 6 further including crimping meansfor crimping selected portions of said rod prior to overwrapping same tyform external cavity means between the outer surface of said rod and theinner surface of said overwrapping material after rod has beenoverwrapped.

1. A method of making smoke filter means comprising: a. providing a bondable filtering material including a multiplicity of fibrous members; b. continuously passing said filtering material into and through an elongated bonding zone and, intermediate the passage of said filtering material through said bonding zone, contacting same with a bonding agent to bond said fibrous members of said filtering material to each other at spaced contact points thereby forming an elongated, smoke-permeable, rod defining a tortuous path for passage of smoke therethrough; c. during the passage of said filtering material through said bonding zone, positioning a mandrel generally axially of said bonding zone to define an annular space through which said filtering material must pass; d. reciprocating said mandrel in timed relationship to the passage of said filtering material through said bonding zone between a first position, at least as far forward in the path of travel of said filtering material as the point at which said filtering material is contacted by said bonding agent, to thereby produce a smoke-permeable annular wall of bonded fibrous members as said filtering passes said point, and a second position, sufficiently rearwardly of said point in the path of travel of said filtering material to permit a portion of said filtering material to extend transversely completely across said bonding zone before reaching sAid point, to thereby produce a smoke-permeable plug of bonded fibrous members as said filtering material passes said point, said annular wall and said plug being integral with each other, whereby said rod is provided with intermittent internal cavities totally enclosed and surrounded by said annular wall and by plugs forwardly and rearwardly thereof; e. overwrapping said rod with an overwrapping material so as to juxtapose portions of the inner surface of said overwrapping material with continuous peripheral portions of the exterior surface of at least portions of selected plugs to form sealed areas precluding passage of smoke thereacross; and f. transversely severing said overwrapped rod at selected locations to form filter elements each of which includes at least one of said internal cavities and at least one of said sealed areas.
 2. A method according to claim 1 wherein said filtering material comprises cellulose acetate tow and said bonding agent comprises steam.
 3. A method according to claim 1 further including the step of feeding a quantity of a sorbent smoke-modifying material through the mandrel during the rearward movement of the mandrel to at least partially fill selected internal cavities with the smoke-modifying material as said internal cavities are formed.
 4. A method according to claim 3 wherein said smoke-modifying material comprises activated carbon.
 5. A method according to claim 1 further including the step of crimping selected portions of said rod before overwrapping same to form external cavities between the exterior surface of said rod and the interior surface of said overwrapping material.
 6. An apparatus for making smoke filter means comprising: a. a source of a bondable filtering material including a multiplicity of fibrous members; b. means defining an elongated bonding zone; c. means for continuously feeding said filtering material into and through said bonding zone; d. means for feeding a bonding agent into said bonding zone and into contact with said filtering material at a point intermediate the path of travel of said filtering material through said bonding zone to bond said fibrous members of said filtering material to each other at spaced contact points, thereby forming an elongated, smoke permeable, rod defining a tortuous path for passage of smoke therethrough; e. elongated mandrel means having a forward end portion axially positioned within said means defining said bonding zone to define an annular space through which said filtering material must pass; f. means for reciprocating said mandrel means within said bonding zone in timed relationship to the passage of said filtering material through said bonding zone between a first position wherein said forward end portion extends at least as far forwardly in the path of travel of said filtering material as the point at which said filtering material is contacted by said bonding agent, to thereby produce a smoke-permeable annular wall of bonded fibrous members as said filtering material passes out said point, and a second position wherein said forward end portion extends sufficiently rearwardly of said point in the path of travel of said filtering material to permit a portion of said filtering material to extend transversely completely across said bonding zone before reaching said point, to thereby produce a smoke-permeable plug of bonded fibrous members as said filtering material passes said point, said annular wall and said plug being integral with each other, whereby said rod is provided with intermittent internal cavities totally enclosed and surrounded by said annular wall and by plugs forwardly and rearwardly thereof; g. means for overwrapping said rod with an overwrapping material so as to juxtapose portions of the inner surface of said overwrapping material with continuous peripheral portions of the exterior surface of at least portions of selected plugs to form sealed areas precluding passage of smoke thereacross; and h. severing means for transversely severing said overwrapped rod at selected locations to form filter elements each of which includes at least one of said internal cavities and at least one of said sealed areas.
 7. An apparatus according to claim 6 wherein said means defining a bonding zone comprises a cylindrical portion and a juxtaposed conical entry portion rearwardly of said cylindrical portion in the path of travel of said filtering material, said means for feeding said bonding agent into said bonding zone comprising a multiplicity of peripherally spaced apertures opening into said cylindrical portion, said forward end portion of said mandrel means in said first position being located at least as far forwardly into said cylindrical portion of said bonding zone as the points at which said bonding agent is fed into said bonding zone, and said forward end portion of said mandrel means in said second position being located within said conical portion of said bonding zone.
 8. An apparatus according to claim 6 wherein said mandrel means is hollow, further including a source of a sorbent smoke-modifying material, and means for feeding said smoke-modifying material through said mandrel means and out of said forward end portion thereof into the cavities being defined in said rod on the rearward stroke of said mandrel means.
 9. An apparatus according to claim 6 further including crimping means for crimping selected portions of said rod prior to overwrapping same ty form external cavity means between the outer surface of said rod and the inner surface of said overwrapping material after rod has been overwrapped. 